The aim of the study was to use the meta-analytic approach to examine the effects of aerobic exercise on C-reactive protein (CRP) in adults. Secondary outcomes included changes in body weight in kilograms, percentage of body fat, and maximum oxygen consumption (VO2max) in mL kg(-1) min(-1). Studies were retrieved using computerized literature searches, cross-referencing, and hand searching. Inclusion criteria were assessment of CRP in randomized controlled trials published in the English language between January 1, 1990, and January 1, 2006. Studies were also limited to aerobic exercise interventions lasting 4 weeks or more in adults 18 years or older. Five studies representing 323 male and female subjects (171 exercise, 152 control) and 6 outcomes for CRP were available for pooling. A nonsignificant reduction of approximately 3% was observed for CRP in the exercise groups (mean +/- SEM, -0.11 +/- 0.14 mg/L; 95% confidence interval [CI], -0.39 to 0.17 mg/L) using a random-effects model. Statistically significant reductions of approximately 4% were found for body weight (mean +/- SEM, -3.4 +/- 1.0 kg; 95% CI, -5.3 to -1.5 kg) and percentage of body fat (mean +/- SEM, -1.4% +/- 0.4%; 95% CI, -2.3% to -0.6%), whereas a statistically significant increase of 12% was found for VO2max (mean +/- SEM, 3.3 +/- 0.9 mL kg(-1) min(-1); 95% CI, 1.5 to 5.1 mL kg(-1) min(-1)). The results of our study suggest that aerobic exercise does not reduce CRP levels in adults, but does improve measures of body composition and physical fitness.